JP2004330192A - Apparatus for discharging coating material - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce possible danger of explosion caused by electric discharge in an apparatus for discharging a coating material. <P>SOLUTION: The apparatus for discharging the coating material is provided with an output port discharging the coating material, electrodes that are installed adjoining the output port and sticking out of the apparatus for discharging so as to give a charge to the coating material discharged from the output port, and a shielding body for shielding a part adjoining a coupling part with the apparatus for discharging in the electrodes. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to the application of articles by electrostatic spraying and charged particles. Although the present application discloses a particular type of coating material dispensing device, it is applicable to a wide variety of coating material applications.

  As used herein, the terms "conductive" and "electrically non-insulating" are used in a broad sense, meaning that they are more conductive than "non-conductive" and "electrically insulating" Means Further, in this specification, terms such as “front”, “rear”, “top”, “bottom” and the like are used only for describing the present invention and do not limit the present invention.

  Various types of automatic hand-held dispensers for coating materials are known. For example, there are guns disclosed in U.S. Pat. Nos. 3,169,882, 3,169,883 and 4,285,446. In addition, REA 3, REA 4, REA 70, REA 90, REM, and M-90 guns are commercially available from ITW Ransburg, located in Toledo, Ohio. Such listing does not mean that all prior arts have been investigated, that there is no better prior art, or that the listed items are patentable material.

  Standard test methods for electrostatic spray dischargers have been published by test organizations in various countries. One example of such a standard is the Electrostatic Finishing Equipment Approval Standard Class 7260 (FM standard) published by the Factory Mutual Research Corporation.

  This FM standard includes procedures for testing hand-operated equipment (eg, spray guns for hand-held coating materials, FM standard chapter 5) and automated equipment (eg, sprayers mounted on robotic arms, FM standard chapter 6). In. Testing in both cases involves probing the instrument at operating voltage using a 1 inch diameter metal earthing body. This test is performed in an atmosphere containing propane in the air. The test fails if exploded. In order to obtain FM certification, the equipment must specifically pass this test. The FM standard has provided significant research and improvement regarding the safety of electrostatic coating systems.

  According to one aspect of the present invention, in a coating material discharging device, an output port that discharges a coating material, and an output port that is disposed adjacent to the output port and is provided so as to protrude from the discharging device, from the output port. There is provided an apparatus for discharging a coating material, comprising: an electrode for providing a charge to the coating material to be discharged; and a shield that shields a portion of the electrode adjacent to a connection portion with the discharging device.

The electrodes may be arranged offset from a central axis of the output port.
The shield comprises a sleeve formed of an insulating material, the sleeve being coupled at a first end thereof to the discharge device, the second of the sleeve having the electrode spaced from the first end. You may make it protrude from an end part.
The electrode may comprise a needle-like electrode.

  According to another aspect of the present invention, in a method of discharging a coating material, a discharging device is provided, an output port is provided in the discharging device, the coating material is discharged from the output port, and the coating material is discharged from the output port. A method for discharging a coating material is provided, comprising: placing an electrode for applying a charge to the coating material adjacent to the output port; and shielding a portion of the electrode adjacent to a discharge device.

The arrangement of the output port may include an arrangement of the output port having a central axis, and the arrangement of the electrodes may include offsetting from the central axis of the output port.
The arrangement of the electrodes may include arranging needle-shaped electrodes.

  Further, shielding of a portion of the electrode comprises providing a sleeve made of an insulating material, coupling the sleeve to the discharge device at a first end thereof, and removing a sleeve of the sleeve spaced from the first end. The electrode can be made to protrude from the end of the second electrode.

  Referring to FIG. 1, in a typical example, a coating material discharge device (hereinafter simply referred to as a "gun") 22 is a REA 3 gun, REA-3, commercially available from ITW Randsburg, Toledo, Ohio. Shows the general shape of type 4 gun, REA 70 type gun, REA 90 type gun, REM type gun and M-90 type gun. The material to be sprayed is supplied from a supply source 24 to an input port 26 of the gun 22 and is provided in front of the gun 22 operated by the trigger 30 via a passage (not shown) provided in the gun 22. It is supplied to a valve (not shown).

  To operate the gun 22, for example, a relatively high DC potential from one or more sources (eg, -85 KV), a relatively low AC or DC potential (eg, ± 12 KV or ± 24 KV; where ± is + Or-), relatively high-pressure air (for example, 100 psi = 0.69 Mpa), relatively constant-pressure air (for example, 20 psi = 0.13 Mpa), or the like is required. Two such sources 29, 31 are shown as such sources. The supply source 29 is a device for supplying compressed air at a desired pressure. The supply source 31 is a relatively low-voltage AC power supply device, for example, a primary transformer provided in the gun 22 and a Cockcroft-Walton multiplier power supply (Cockcroft-Walton multiplier power supply) 33 (hereinafter referred to as an internal power supply 33). To be described). Although a relatively low DC voltage may be applied to the gun 22, an inverter must be incorporated in the built-in booster 33 to convert low-voltage DC to AC for boosting and double voltage rectification. For example, built-in booster 33 includes a system implemented with REA 90 and REA 90L guns available from ITW Ransburg, Toledo, Ohio. Other types of power supplies may be used. For example, power can be generated by a turbine driven by compressed gas disposed in the gun and supplied to a primary transformer and a Cockcroft-Walton doubler. At that time, when generating AC in the gun, supply it directly to the primary transformer and Cockcroft-Walton type voltage doubler rectifier, and when generating DC in the gun, use the inverter to convert the primary transformer and Cockcroft. -Supply to Walton type voltage doubler. The application material is sprayed at a nozzle 34 of the gun 22 by being operated by the trigger 30, and is discharged from the nozzle.

  The output from the built-in booster 33 is coupled to a needle-like charging electrode (needle electrode) 40 via a circuit provided in the gun 22. The needle electrode is mounted on an air cap 36 provided at the front of the gun 22. The air cap 36 houses the nozzle 34. In this way, an electric field is formed between the needle electrode 40 and a nearby grounded object, for example, a grounded article 42 to be coated with a coating material emitted from the gun 22. The sprayed particles of the coating material are charged by the electrons from the needle electrode 40 according to the established principle, move to the article 42 along the electric field, and adhere to the article 42.

  During testing according to the standard, the area around the nozzle 34 is examined with a 1 inch (about 2.5 cm) diameter grounded sphere 43 while high voltage is applied to the needle electrode 40. When the sphere 43 moves forward, for example, from the gun 22 toward the air cap 36 near the needle electrode 40, a corona discharge occurs between the sphere 43 and the needle electrode 40. In the prior art configuration, however, a relatively high-energy corona discharge occurs in the base end region of the needle electrode 40, that is, in the portion where the needle electrode 40 protrudes forward from the front surface of the air cap 36. This corona discharge is formed between a small area of the sphere 43 and the base end of the needle electrode 40. Such relatively high energy corona discharges in prior art arrangements are sufficient to ignite propane contained in an air mixture as defined by the FM standard and, needless to say, do not meet the FM standard.

  According to the present invention, a sleeve 46 made of an insulating material is disposed around the needle electrode 40 and the needle electrode 40 is directed toward the metal earth 43 approaching the gun 22 from any angle. Shield the needle electrode from high energy discharge from the proximal end. The discharge formed from the shielded needle electrode 40 occurs from the tip of the needle electrode 40 and the unshielded region 48 adjacent to the tip. In the gun 22 having the needle electrode 40 shielded by the sleeve 46, a high-energy discharge is generated very little, and the test result specified by the FM standard is further improved.

  In the illustrated embodiment, needle electrode 40 is a 0.016 inch (about 0.4 mm) diameter titanium electrode that projects about 0.25 inch (about 6.4 mm) forward from the front surface of air cap 36. I have. The air cap itself is made of acetal resin having a trade name of black type 150E Delrin brand. The sleeve 46 may be made of a suitable insulating material such as polyetheretherketone (PEEK) resin, acetal resin, for example, Delrin (trademark) acetal resin, lithium tetrafluoroethylene (PTFE), for example, Teflon (trademark) PTFE, polyamide, for example, nylon. It is formed to an appropriate length from the material. Sleeve 46 has an inner diameter of about 0.20 inches (about 0.5 mm) and an outer diameter of about 0.0625 inches (about 1.6 mm). The sleeve 46 also has a length such that the exposed pointed portion 48 of the needle electrode 40 projects about 0.05 inch (about 1.27 mm). The same portion (or all portions) in the longitudinal direction of the needle electrode 40 may be coated (conformal coating) to an appropriate thickness, for example, 0.001 inch (about 0.03 mm). When coating all portions of the needle electrode 40, the tip portion of the needle electrode is treated so as to be exposed so as to form a point for charging.

  The sleeve 46 can be adhered to the air cap 36 so as to surround the proximal end portion of the needle electrode 40 using an adhesive suitable for a material forming the sleeve 46. For example, if the sleeve 46 is formed from PEEK resin, a cyanoacrylate adhesive such as Zip Frip 4495, commercially available from ITW Devcon, is applied to the outer surface of the sleeve 46. Alternatively or additionally, sleeve 46 may be pressure fitted to needle electrode 40 and / or surround the proximal end of needle electrode 40 at air cap 36 to couple sleeve 46 to air cap 36. It may be press fit into a recess (not shown).

  Although the needle electrode 40 is illustrated as being offset from the center axis of the air cap 36, the present invention is directed to the case where the needle electrode projects from the approximate center of the air cap 36, i.e., the center of the barrel 35 of the gun 22. Is also applicable.

  It is believed that the device according to the invention gives good results when tested according to the FM standard, because the high-voltage discharge has a tendency to proceed along the available surface. The insulation shielding by the sleeve 46 may be such that the discharge must travel a longer distance from the exposed tip 48 of the needle electrode 40 to a nearby grounded surface, such as the sphere 43, or if the sleeve 46 is not provided. This means that the dielectric strength of the sleeve 46 must be overcome in order to discharge the same distance.

It is a side view showing a spray gun to which the present invention is applied. FIG. 2 is a side view of an air cap of the spray gun of FIG. 1. FIG. 3 is a front view of the air cap as viewed in the direction of arrow 3-3 in FIG. 2. FIG. 4 is a rear view of the air cap as viewed in the direction of arrow line 4-4 in FIG. 2. FIG. 5 is a cross-sectional view of the air cap taken along line 5-5 in FIG. 4.

Explanation of reference numerals

22 ... Discharge device (gun)
Reference numeral 24: supply source of the coating material 26: input port 29: supply source of the compressed air 30: trigger 31, power supply device 33, built-in booster 34, nozzle 36, air cap 40, needle electrode 42, article

Claims (9)

In the coating material discharging device,
An output port for discharging the coating material,
An electrode that is disposed adjacent to the output port and protrudes from the emission device, and that applies an electric charge to the coating material emitted from the output port; And a shield for shielding a portion to be coated.   The discharge device according to claim 1, wherein the electrode is offset from a center axis of an output port.   The shield comprises a sleeve formed of an insulating material, the sleeve coupled to the emission device at a first end thereof, and the electrode is connected to a second one of the sleeves spaced from the first end. 3. Discharge device according to claim 2, protruding from the end.   The discharge device according to claim 1, wherein the electrode comprises a needle-like electrode.   The shield comprises a sleeve formed of an insulating material, the sleeve coupled to the emission device at a first end thereof, and the electrode is connected to a second one of the sleeves spaced from the first end. 5. The discharge device according to claim 4, protruding from an end of the discharge device. In the method of releasing the coating material,
Prepare the discharge device,
Disposing an output port on the discharge device;
Discharging the coating material from the output port,
An electrode that gives a charge to the coating material discharged from the output port is disposed adjacent to the output port,
A method for discharging a coating material, comprising shielding a portion of the electrode adjacent to a discharging device.   7. The method of claim 6, wherein disposing the output port comprises disposing an output port having a central axis, and disposing the electrode comprises offsetting from the central axis of the output port.   7. The emission method according to claim 6, wherein the disposing of the electrodes includes disposing a needle-like electrode. Shielding the part of the electrode, providing a sleeve made of an insulating material;
9. The discharge of claim 8, comprising coupling the sleeve to the discharge device at a first end thereof, the electrode protruding from a second end of the sleeve spaced from the first end. Method.

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